Lipids Flashcards
Hydrolytic Rancidity: main chemical reaction (type)?
Hydrolysis of the ester bond between glycerol and fatty acid
Note: the oxidation state is not affected
Hydrolytic Rancidity: What are the products?
Glycerol and free fatty acids
Hydrolytic Rancidity: what speeds up the process?
Heat, water content, lipases
Hydrolytic Rancidity: What foods are particularly affected (and why)?
Foods that undergo frying and foods with high lipase activity
Oxidative Rancidity: main chemical reaction (type)?
Hydrogen abstraction from a CH2 group next to or, if available, in between DBs on a FA, followed by attachment of O2. Overall, the lipid is oxidized
Oxidative Rancidity: What are the products?
- Hydroperoxides
2. Mostly ketones and aldehydes from ROOH decomposition
Oxidative Rancidity: What speeds up the process?
Heat, light, redox-active metal ions, lipoxygenases
Oxidative Rancidity: What foods are particularly affected (and why)?
Foods that contain PUFAs, because the CH2 group in between DBs is attacked preferentially
Antioxidant Properties of Citric Acid
Citric acid is a metal chelator, and prevents redox reactive metals such as Fe and Cu from initiating or promoting lipid oxidation
Antioxidant Properties of BHT
BHT is a phenolic radical scavenger. It forms
resonance-stabilized radicals that do not attack fatty
acids, but rather recombine with other radicals
Diacylglycerols are less polar than monoacylglycerols
T/F
True
Monoacylglycerols are the most polar simple lipid
Butanoic acid is more polar than palmitic acid
T/F
True
Butanoic acid is a short chain saturated fatty acid and has partial solubility in water. This is because it is more polar than the palmitic (LCFA) that is practically insoluble in water
α-linolenic acid is more unsaturated than γ-linolenic acid T/F
False
They have the same amount of saturation (3 DB)
α-linolenic acid is essential while stearic acid is not
T/F
True
α-linolenic acid is one of the 2 essential FA
The shorthand notations 18:1 ω9 and 18:1 ∆9 describe the same fatty acid T/F
True
They both describe oleic acid
Which of the following conditions do not accelerate lipid oxidation A. Light B. Moisture levels below the monolayer C. Moisture levels at the monolayer D. Temperature E. Presence of Fe2+ F. Presence of Ca2+
B,C,F
Rank the following fatty acids in terms of increasing melting point A. Linoleic acid B. Oleic acid C. Myristic acid (C14:0) D. Stearic acid E. Arachidic acid (C20:0) F. Docosahexaenoic acid
Lowest to highest BP
F,A,B,C,D,E
